Process of making liquid leather-dressing from tanning-liquors.



GEORGE W. C HILDS, OF NEW YORK, N. Y.

PROCESS OF MAKING LIQUID LEATHER-DRESSING FROM TANNING' LIQUORS.

Specification of Letters Patent.

Patented March 17, 1908.

Application filed September 24, 1907. Serial No. 394,803.

T 0 all whom it may concern:

Liquid I.eatherDressings from Tanning Liq uors, whereof the following is a specification.

The leather dressing produced by the process herein claimed is particularly applicable to the manufacture of leather, such as sole leather, which it is desired shall attain the greatest degree of solidity possible with the necessary degree of flexibility. All processes for making such leather have heretofore involved two stages :First, the hides are subjected to the action of a liquor comprising active tannic material until combined with all of the tannin with which they are capable of combining and, second, the leather thus tanned is then subjected to a loading process, which usually consists in impregnating the leather with concentrated bark extract.

The leather dressing hereinafter described is adapted to impregnate hides contemporaneously with an active tannic material and with an inert (non-tannic) loading material so that the required effect is produced in much less time than if said materials were applied successively as heretofore, and, said inert loading material being less costly than the active tannic material heretofore employed for loading purposes, the cost of the dressed leather is correspondingly less than heretofore. Said dressing is conveniently formed by mixing sapped or exhausted tanning liquor containing a high percentage of inert solid matter, with fresh tanning liquor containing active tannic material, and then concentrating the mixture until it is from 1.05 to 1.3 specific gravity.

I prefer to employ waste tanning liquors which are devoid of the acid or alkaline impurities which are usually found in such liquors. F or instance, if the Waste liquor is from an acid tanning yard, and contains sulfuric or other non-volatile mineral acid, it may be neutralized by the addition of alkali, for instance sodium hydrate, or potassium hydrate, or, the acids may be precipitated as salts by the addition of bases forming insoluble compounds with the acids; for instance, barium chlorid. If the Waste liquor is from a non-acid yard and contains lime or lime compounds, such impurities may be precipitated by the addition of chemicals forming insoluble compounds with lime for instance, ammonium oxalate, sodium phosphate, sodium fluorid, or carbon dioxid gas may be employed to effect such precipitation. On the other hand, if the waste liquor does not contain the mineral impurities aforesaid, but contains volatile impurities, for instance, volatile acids, such impurities may be eliminated by heating the liquor. The waste liquor may be mixed with fresh tanning liquor or bark extract and then concentrated, conveniently by heating in vacuo, until it is from 1.05 to 1.3 specific gravity. it may be observed that if said dressing were of less specific gravity, there would not be suflicient solid residue thereof when the leather is dried to obtain the result desired. Moreover, if said dressing were of a greater specific gravity it would not be absorbed by the leather.

Said dressing may be utilized as follows Hides which have been treated in vats with any suitable tanning solution until they are colored through, are placed in a rotary drum, and said dressing, preferably heated, introduced to said drum, conveniently throu h a hollow axle or trunnion thereof, and t e revolution of said drum continued until said dressing is absorbed by the hides. The hide substance having then combined with all of the tannin with which it will combine, and the pores of the leather being filled with said dressing; when dried, the residue of the dressing in the leather not only renders the latter more solid than if it had not been impregnated with said dressing, but also adds materially to its final weight. as last described, may then be bleached oiled, dried, dampened and rolled in the usual manner.

A process for treating Waste tanning liquor containing mineral acid impurities, as above contemplated, forms the subject matter of my app ication Serial #317,141, filed May 16, 1906, for Letters Patent of the United States, and, a process for treating leather with concentrated waste tanning liquor, as above contem lated, forms the subject matter of my app ication Serial #327,029, filed July 20, 1906, for Letters Patent of the United States.

I do not desire to limit myself to all of the details of procedure above enumerated, as various modifications may be made therein Leather treated without departing from the essential features of my invention, as defined in the appended claims. 1 I claim: 1. The process of making leather dressing hi 11 consists in waste tanning liquor with active tanning material and concentrating themixture until it is from "1.05 to 1.3 specific gravity. 1

2. The process of making leather dressing from tanning liquors, which consists in m xi ing waste tanning liquor with active tanning liquor and concentrating the mixture until it GEORGE W. CHILDSQ- Witnesses:

HENRY W. HEALY, M10. P. ANDERSON. 

